Percentage Calculator
Six-mode percentage tool — X% of Y, X is what % of Y, % change, % difference (symmetric), add %, and subtract %.
Result
- As fraction0.2500 × 200
- In money$50.00
How to use this calculator
- Pick the mode that matches your question.
- Type the two numbers — labels adapt based on mode.
- Read the primary result + secondary breakdowns.
About this tool
Six percentage problems in one tool, because most "percentage calculators" only do one. Mode 1: classic "what is 15% of $80" (the answer is $12). Mode 2: "$45 is what % of $200" (22.5%). Mode 3: percentage change between two values — useful for "stock went from $50 to $73, what %?" (+46%). Mode 4: percent difference — the order-independent variant used in scientific writing, |A−B| ÷ average × 100. Mode 5: add X% to Y — markup, sales tax, percentage raises. Mode 6: subtract X% from Y — discounts, depreciation, sale prices. Mode 3 also shows the reverse change, which is NOT the same number — going from $73 back to $50 is a 32% decrease, not 46%, because the denominators differ.
What this calculator does
This is three percentage tools in one. Mode 1 answers "what is X percent of Y" — the classic discount or tax question. Mode 2 answers "X is what percent of Y" — the share-of-whole question. Mode 3 answers "what is the percent change from A to B" and includes the reverse change, which is rarely the same number because the denominator shifts. The output includes the decimal equivalent (useful for Excel and statistics work) and a multiplier (1.46× for a 46% increase), so the same answer is presented in whichever shape your downstream workflow wants.
How it works — the formula
pct_of: result = (X / 100) · Y
is_what: pct = (X / Y) · 100
change: pct = ((B − A) / A) · 100Percentages are ratios scaled to a base of 100. Mode 1 is the definition. Mode 2 is the definition rearranged. Mode 3 normalises the absolute change by the starting value — and because the starting value changes between A→B and B→A, the two percent changes are different. NIST defines "percent" and "percentage point" as separate quantities; conflating them is one of the most common reporting errors in financial and statistical writing.
Worked examples
- Inputs:
- X = 15, Y = 80 ("what is 15% of 80?")
- Output:
- result = 12 (decimal 0.15 × 80)
The everyday "what is X% of Y" question — sales tax, tips, sale discounts, commissions. Mode 1 is by far the most-used percentage operation.
- Inputs:
- X = 45, Y = 200 ("45 is what % of 200?")
- Output:
- 22.5%; decimal 0.225
Share-of-whole questions: market share, exam scores, conversion rates. The reciprocal is also surfaced — 200 is 444% of 45.
- Inputs:
- A = 50, B = 73 ("$50 stock went to $73")
- Output:
- +46% increase; multiplier 1.46×; reverse change −32%
Percent change is asymmetric. A +46% gain requires a −32% loss to return to start, NOT a −46% loss. This is the source of the "you lose more than you make" intuition behind sequence-of-returns risk.
When to use this vs other tools
Percentage Calculator is the general-purpose tool. Use a specialised calculator when the domain has its own conventions.
- Markup Calculator
Use for retail / pricing — markup (percent added to cost) and margin (percent of price kept as profit) are different operations from a plain percent and have their own conventions.
- Tip Calculator
Use for restaurant tipping with an n-way split. Tip is just "Mode 1 — percent of bill" plus a divide-by-n; the dedicated tool also surfaces 15/18/20% reference lines.
- Inflation Calculator
Use for real-vs-nominal comparisons across years. Inflation Calculator pulls BLS CPI series, so a 1990-vs-2025 comparison uses the right cumulative percent change, not a single annual rate.
- Investment Return Calculator
Use for annualised returns on multi-year investments — a single percent change over five years is not the same as a CAGR, and confusing the two is a common reporting error.
Authority note
NIST SP 811 is the US authoritative reference for percent vs percentage-point usage in scientific and technical writing. The same distinction is enforced in BLS, Federal Reserve, and IMF reporting conventions.
Limitations
- Percent and "percentage point" are not the same — when the underlying quantity is itself a percent (interest rate, tax rate, unemployment), always state which you mean.
- Percent change is asymmetric: a +X% then −X% does not return to the start. The reverse-change line in Mode 3 makes this explicit.
- Percent of negative numbers is mathematically well-defined but produces signs that may be unintuitive in the breakdown row.
- For multi-period growth comparisons, an annualised (CAGR) figure is more useful than a raw single percent change — use the Investment Return Calculator instead.
This calculator is a general-purpose arithmetic tool. It does not provide financial, tax, or investment advice; check the domain-specific calculators for context-aware figures.